Fix setuptools-scm version for Python 3.6 (#440)

CHANGELOG.md

@@ -11,6 +11,8 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 -   Update `docker/setup-qemu-action` GitHub action to v2
 -   Fixed CentOS 7 configuration issue
+-   Remove deprecated `setup_requires` field in setup.cfg
+-   Fixed installation issue with newer versions of `setuptool-scm`and Python¨ 3.6
 
 ## [v0.7.3] - 2022-04-27
 

pyproject.toml

@@ -1,5 +1,7 @@
 [build-system]
-requires = ["setuptools>=42", "wheel", "pybind11>=2", "setuptools_scm[toml]>=3.4"]
+requires = ["setuptools>=42", "wheel", "pybind11>=2",
+            "setuptools_scm[toml]<7;python_version<'3.7'",
+            "setuptools_scm[toml]>6;python_version>='3.7'"]
 build-backend = "setuptools.build_meta"
 
 # ==============================================================================

setup.cfg

@@ -31,9 +31,6 @@ classifier =
 zip_safe = False
 packages = find:
 python_requires = >= 3
-setup_requires =
-  setuptools_scm[toml]
-  pybind11 >= 2
 install_requires =
     matplotlib >= 2.2.3
     networkx >= 2

setup.py

@@ -58,6 +58,14 @@
 from setuptools import Extension, setup
 from setuptools.command.build_ext import build_ext
 
+try:
+    import setuptools_scm  # noqa: F401  # pylint: disable=unused-import
+
+    _HAS_SETUPTOOLS_SCM = True
+except ImportError:
+    _HAS_SETUPTOOLS_SCM = False
+
+
 # ==============================================================================
 # Helper functions and classes
 
@@ -645,9 +653,12 @@ def run_setup(with_cext):
     else:
         kwargs['ext_modules'] = []
 
+    # NB: Workaround for people calling setup.py without a proper environment containing setuptools-scm
+    #     This can typically be the case when calling the `gen_reqfile` or `clang_tidy`commands
+    if not _HAS_SETUPTOOLS_SCM:
+        kwargs['version'] = '0.0.0'
+
     setup(
-        use_scm_version={'local_scheme': 'no-local-version'},
-        setup_requires=['setuptools_scm'],
         cmdclass={
             'build_ext': BuildExt,
             'clang_tidy': ClangTidy,